General Manager A.J. Smith has a vision for the Chargers defense, he says, and he may have just added a big piece.

On Thursday, with the 18th pick in the first round, the Bolts selected South Carolina’s Melvin Ingram, an athletic defensive end who’ll play outside linebacker in the team’s 3-4 scheme.

Smith called him a “mean, nasty man — extremely physical with a great motor.”

And he was a pleasant surprise.

The 6-foot-1, 276-pounder, by many analysts’ accounts, was the top-rated pass rusher in the draft and expected to be long gone by pick 18. Yet there he was.

Following the pick, the TV talking heads called it “a steal,” “the greatest value so far,” “the best pick of the middle of the draft.”

Of course, time will have the final say.

“We talked earlier today, if he was there, what do we do?” coach Norv Turner said. “We could take him. There’s some other guys. You have to have a plan. We just felt he was there, you wouldn’t do anything other than (take him).”

Ingram, who was celebrating his 23rd birthday, called it the best present he’s ever received “by far.”

“I’ve been thanking God a million times just to have the opportunity to be part of a winning organization,” Ingram said in a video conference call from New York City. “I feel I can bring a hard worker who’s going to lay it on the line every play for my teammates, who’s going to have a relentless effort. I’m going to learn the playbook as soon as possible to get on the field as soon as possible.”

As a senior in 2011, Ingram started all 13 games for the Gamecocks, totaling 10 sacks with six pressures. In 2010, he had nine sacks in 14 games with one start.

Ingram earned the nickname “Super Melvin” in high school for being able to play so many positions, and the moniker stuck at South Carolina, where he played defensive tackle, defensive end and linebacker.

The Chargers can line him up all over the field.

Currently on their roster, outside linebackers Shaun Phillips, Antwan Barnes and Travis LaBoy are in the final year of their contracts. The trio accounted for 45 percent of the team’s quarterback pressures in 2011.

As a unit, San Diego’s defense allowed a 49.2-percent conversion rate on third downs, worst in the NFL since 1995.

“We have a lot of work to do,” Turner said. “When you’re 32nd in the league on third down, it’s not one thing. But to me, it starts with pressuring the quarterback, and the other end of it, obviously, is as you’re getting pressure, find a way to get enough coverage so the quarterback has to hold onto the ball.